﻿#region License
// Copyright 2009 Buu Nguyen (http://www.buunguyen.net/blog)
// 
// Licensed under the Apache License, Version 2.0 (the "License"); 
// you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at 
// 
// http://www.apache.org/licenses/LICENSE-2.0 
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, 
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
// See the License for the specific language governing permissions and 
// limitations under the License.
// 
// The latest version of this file can be found at http://dotcommon.codeplex.com
#endregion

using System.IO.Compression;
using System.Web.Mvc;

namespace DotCommon.Mvc
{
    /// <summary>
    /// Filter to compress output of action or controller.
    /// </summary>
    public class CompressResponseAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            var acceptedEncodings = filterContext.HttpContext.Request.Headers["Accept-Encoding"];
            if (string.IsNullOrEmpty(acceptedEncodings)) 
                return;
            var response = filterContext.HttpContext.Response;
            
            // Tells proxy to cache different versions depending on Accept-Encoding 
            response.Cache.VaryByHeaders["Accept-Encoding"] = true;
            if (acceptedEncodings.Contains("deflate"))
            {
                response.AppendHeader("Content-Encoding", "deflate");
                response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
            }
            else if (acceptedEncodings.Contains("gzip"))
            {
                response.AppendHeader("Content-Encoding", "gzip");
                response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
            }
        }
    }
}
